1. Field of the Invention
The present invention relates to a web joining apparatus and a method and particularly to a web joining apparatus and a method for joining a thin-plate band-state material such as plastic, paper, metal foil, etc. (hereinafter referred to as “web”) in the state where ends of a new and an old rolls are overlapped with each other.
2. Description of the Related Art
A conventional web joining apparatus in general is an apparatus of a so-called face-to-face joining type by which a tail end of an old web and a tip end of a new web is abutted to each other at joining and joined in that state by pasting them through extension of a joining tape to the both (See Japanese Examined Application Publication No. 48-38461, for example). This type of apparatus has a long history of operation and is still in use after repeated improvements (See Japanese Patent Application Laid-Open No. 6-171806, for example).
The face-to-face web joining apparatus described in this Japanese Patent Application Laid-Open No. 6-171806 is a three-drum type apparatus comprising a cutting drum provided with a cutting blade and a member for withdrawing a web tip end of a new roll and capable of rotation at the same speed as a conveying speed of the web, a cutting/joining drum capable of rotation at the same speed as the conveying speed of the web, and a joining drum detachably holding a joining tape and capable of rotation at the same speed as the conveying speed of the web, wherein the webs are cut off and joined while the tail end of the old roll and the tip end of the new roll are held at each of the drums so that the webs can be cut and joined at a high speed.
However, in the conventional face-to-face web joining apparatus, there is a problem that it is not suitable for a process requiring high cleanliness (degree of cleanness) (such as a manufacturing process of a functional film used in a liquid crystal display device).
Specifically, in the apparatus of the above Japanese Patent Application Laid-Open No. 6-171806, for example, a guide member with a triangular section for guiding the web at joining so that it does not deviate from a web conveying path is provided in a space portion in the substantially triangular shape surrounded by rotating outer circumferences of the cutting drum, the cutting/joining drum and the joining drum. But this guide member is rubbed by the web, which often generates contamination such as dusts.
Moreover, the old roll web is rubbed by the new roll web, which generates contamination such as dusts in many cases.
However, if a measure is to be taken against these problems, it is difficult to exclude the guide member and the like from the viewpoint of the principle of face-to-face abutting of the webs, and it is also difficult to employ a construction to prevent rubbing between the old roll web and the new roll web, for which improvement by other devices has been in demand.
The present invention was made in view of these circumstances, and its object is to provide a web joining apparatus and a method which can improve joining accuracy without generating contamination such as dusts so as to be applied to a process requiring high cleanliness (degree of cleanness) and can improve web quality.